Rocephin (Ceftriaxone) Dosing for 15-Year-Old, 56kg Patient
For a 15-year-old weighing 56kg, administer ceftriaxone 50-100 mg/kg/day (2.8-5.6 grams) once daily or divided every 12 hours, with the specific dose depending on infection severity—use 50-75 mg/kg/day for moderate infections and 100 mg/kg/day for severe infections or meningitis, not to exceed the adult maximum of 4 grams daily. 1, 2
Dosing Algorithm by Infection Severity
For Moderate/Non-Severe Infections
- Administer 50-75 mg/kg/day (2.8-4.2 grams for this 56kg patient) given once daily or divided every 12-24 hours 1
- This dosing range is appropriate for community-acquired pneumonia, complicated intra-abdominal infections, and sepsis without severe features 1
For Severe Infections
- Administer 80-100 mg/kg/day (4.5-5.6 grams for this 56kg patient) given once daily or divided every 12 hours 1
- The higher dosing range is indicated for severe sepsis, pneumococcal pneumonia with penicillin resistance (MIC ≥4.0 μg/mL), and critically ill patients 1, 2
For Bacterial Meningitis
- Administer 100 mg/kg/day (5.6 grams for this 56kg patient) divided every 12-24 hours 1, 2
- This represents the maximum recommended pediatric dose for CNS infections 1
Critical Maximum Dose Limitation
The pediatric dose must not exceed the adult maximum of 4 grams daily, regardless of weight-based calculations. 1 For this 56kg patient:
- Weight-based calculations would suggest 2.8-5.6 grams daily
- However, doses must be capped at 4 grams daily maximum 1
- Therefore, practical dosing is 2-4 grams daily depending on infection severity
Age-Specific Considerations
- At age 15 years, this patient is at the transition point where adult dosing begins 3
- Children weighing more than 40kg should generally be dosed as adults 3
- For this 56kg adolescent, adult dosing parameters apply with the 4-gram daily maximum 1
Administration Recommendations
Route Selection
- Both intravenous and intramuscular routes are acceptable 3, 4
- Intramuscular injection is painful—counsel the patient accordingly and inject deep into a large muscle mass 1, 5
- IV infusion should be administered over 30 minutes 4
Dosing Frequency Options
- Once-daily dosing is effective and convenient for most infections 1, 6, 7
- Twice-daily dosing (divided every 12 hours) improves target attainment in patients with high estimated glomerular filtration rate (>80 mL/min/1.73 m²) or when treating less-susceptible pathogens (MIC ≥0.5 mg/L) 8
Common Pitfalls to Avoid
- Do not use calcium-containing diluents (Ringer's solution, Hartmann's solution) as ceftriaxone-calcium precipitation can occur 5
- Do not exceed 4 grams daily even though weight-based calculations may suggest higher doses 1
- Do not use the lower dosing range (50 mg/kg/day) for severe sepsis or meningitis—these require 80-100 mg/kg/day 1
- For suspected staphylococcal infections, ceftriaxone alone may be inadequate—add anti-staphylococcal coverage 1